package com.github.fancyideas.utils;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.HashSet;
import java.util.Set;

public class UpdateWithoutNull<T extends JpaRepository, K> {

    public K updateParameterWithoutNull(T t, K toUpdate, Long id) {
        K fromDataBase = (K) t.findById(id).get();
        BeanUtils.copyProperties(toUpdate, fromDataBase, getNullPropertyNames(toUpdate));
        return (K) t.save(fromDataBase);
    }

    private String[] getNullPropertyNames(Object source) {
        final BeanWrapper src = new BeanWrapperImpl(source);
        java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();

        Set<String> emptyNames = new HashSet<>();
        for (java.beans.PropertyDescriptor pd : pds) {
            Object srcValue = src.getPropertyValue(pd.getName());
            if (srcValue == null) emptyNames.add(pd.getName());
        }
        String[] result = new String[emptyNames.size()];
        return emptyNames.toArray(result);
    }

}
